With the growth of the wireless communications industry, wireless communications systems have become more sophisticated, and may have to provide support for multiple communications protocols. One example is a system requiring support for both the Wide Band Code Division Multiple Access (WCDMA) and the Global System for Mobile Communications (GSM) communications protocols. These two protocols have significant differences such that two different RF transceivers may be needed. FIG. 1 shows a dual transceiver communications system 10 using a common antenna 12 coupled to antenna connections ANT of a first antenna switch branch 14 and a second antenna switch branch 16. A radio connection RADIO of the first antenna switch branch 14 is coupled to a first transceiver 18, which may provide support for the GSM protocol. A radio connection RADIO of the second antenna switch branch 16 is coupled to a second transceiver 20, which may provide support for the WCDMA protocol. A control system 22 selects either the GSM or the WCDMA protocol by enabling either the first antenna switch branch and transceiver 14, 18 or the second antenna switch branch and transceiver 16, 20. A control input CONTROL of the second antenna switch branch 16 receives a control signal from the control system 22. A control input CONTROL of the first antenna switch branch 14 receives the control signal from the control system 22 through an inverter 24. Therefore, when the first antenna switch branch 14 is enabled, the second antenna switch branch 16 is disabled, and vice versa. The control signal may be low voltage in the range of about 2.5 volts. The antenna switch branches 14, 16 may have similar construction.
When transmitting and receiving using the GSM protocol, the first antenna switch branch 14 is enabled and the second antenna switch branch 16 is disabled. The GSM protocol may support a transmitter output power of about +33 decibel milliwatts (dbm); therefore, the enabled first switch branch 14 must be capable of transferring +33 dbm of power to the antenna 12. The disabled second switch branch 16 must present substantially an open circuit in the presence of +33 dbm signals.